field-testing the maestro space instrument concept
TRANSCRIPT
Measurements of O2, O3, and NO2 During the MANTRA Balloon Campaign: Field-Testing the MAESTRO Space Instrument Concept
Caroline R. Nowlan1*, James R. Drummond1, C. Thomas McElroy2, Clive Midwinter2, Kimberly Strong1, and David S. Turner2
1. Department of Physics, University of Toronto, 60 St. George Street, Toronto, Ontario, Canada, M5S 1A72. Meteorological Service of Canada, 4905 Dufferin Street, Downsview, Ontario, Canada, M3H 5T4
The MAESTRO (Measurement of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation) satellite instrument will accompany the Atmospheric Chemistry Experiment Fourier Transform Spectrometer on the Canadian satellite SciSat-1 when it is launched in December 2002. MAESTRO is a photodiode array spectrometer that will make solar occultation measurements of atmospheric attenuation during satellite sunrise and sunset to investigate the dynamical and chemical processes affecting stratospheric ozone. The precursor instrument to MAESTRO, the Composition and Photodissociative Flux Measurement instrument, was launched on August 29, 2000 from Vanscoy, Saskatchewan as part of the main high-altitude balloon payload during the MANTRA (Middle Atmosphere Nitrogen TRend Assessment) 2000 field campaign. Sunrise occultation measurements made from a float altitude of 37 km have resulted in the retrieval of vertical profiles of ozone and nitrogen dioxide. Of particular relevance to the MAESTRO project are measurements of the A and B bands of molecular oxygen, which will be used for retrieving vertical profiles of atmospheric temperature and pressure on orbit. Molecular oxygen measurements made during the MANTRA campaign will be used to validate fast line-by-line models for MAESTRO temperature and pressure retrievals.
1. MAESTRO AND MANTRA SCIENCE GOALS
The MAESTRO instrument has an extensive design heritage in several instruments developed at the Meteorological Service of Canada. Its immediate precursor instrument is the CPFM (Composition and Photodissociative Flux Measurement) instrument which has flown on numerous NASA ER-2 campaigns (McElroy, 1995), and several high-altitude balloon flights.
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A32B-0055AGU Fall Meeting
December 10-14, 2001San Francisco
3. INSTRUMENT DETAILS
• Spectral Range: � ultraviolet, visible, and near-infrared� 285 to 785 nm
• Instrument has two main components� Concave mirror with superimposed grating� Photodiode array detector with 1024
individual randomly-addressable pixels• 1 nm resolution• Uses filter wheels for measuring visible/near-
IR (from first-order diffraction) or UV (from second-order diffraction) spectra
• MAESTRO’s design is very similar to the CPFM, but the MAESTRO instrument has two independent spectrometers working in the first-order: one from 285 to 550 nm and another from 525 to 1030 nm.
2. MANTRA BALLOON CAMPAIGN
• The CPFM instrument was launched on the main balloon payload of the MANTRA (Middle Atmosphere Nitrogen TRend Assessment) campaign, on August 29, 2000 from Vanscoy, Saskatchewan, Canada.
• The instrument was fixed to a solar pointing system (Quine et al., 2001), which allowed solar occultation measurements to be made from a float altitude of 37 km during sunrise.
• Other instruments on the payload included chemical and UV ozonesondes (for ozone profile comparisons), a radiosonde (for temperature and pressure profile comparisons), an aerosol sonde, and two emission radiometers.
• A limb scan was performed when the Sun was high in the sky.
REFERENCESMcElroy, C. T., A spectroradiometer for the measurement of direct and scattered solar irradiance from on-board the NASA ER-2 high-altitude research aircraft, Geophys. Res. Lett., 22, 1361-1364, 1995.
Miller, A. J., and M. C. Pitts, SAGE III Algorithm Theoretical Basis Document: Temperature and Pressure Data Products, NASA ESE Doc., 71 pp., NASA Langley Research Center, Hampton, VA, 2000.
Quine, B. M., K. Strong, A. Wiacek, D. Wunch, J. A. Anstey, and J. R. Drummond, Scanning the Earth’s limb from a high-altitude balloon: the development and flight of a new balloon-based pointing system. Accepted by J. Atmos. Oceanic Technology, October 2001.
ACKNOWLEDGEMENTS
We wish to acknowledge the Canadian Space Agency and the Natural Sciences and Engineering Research Council of Canada for their support. We would also like to thank Bob Hall, Aaron Ullberg, and Dave Barton of the Meteorological Service of Canada for help in the field, and the entire MANTRA team for making the mission enjoyable and a success.
4. DATA AND ANALYSIS
Calibrated spectra were produced from the raw data by accounting for the effects of instrument response, stray light, dark current drift with temperature, and pixel bias (McElroy, 1995).
Figure 4. Optical layout of CPFM & MAESTRO
instruments
Figure 5. The CPFM instrument with external cover removed.
The longest dimension is approximately 15 cm.
Figure 1. Absorption by molecular oxygen in the three bands of interest for temperature and pressure retrievals, for a tangent height of 20 km. The blue line shows the absorption at moderate resolution (0.05 nm), while the red line
is that absorption convolved with the slit function of the instrument.
Temperature and Pressure Measurements
On-orbit temperature and pressure profiles are desirable for accurate retrievals of aerosols and gas species from the MAESTRO space instrument, as well as for incorporation into dynamical and climatological models of the atmosphere. In order to derive these parameters spectroscopically, the absorption of a well-mixed gas must be measured. The feasibility of using the A-band of molecular oxygen for temperature and pressure retrievals from a UV/visible grating spectrometer has been previously demonstrated (Miller and Pitts, 2000). MAESTRO will use the A-band for high tangent height measurements, and the B and γ-bands for the lower atmosphere where the A-band saturates.
For accurate temperature and pressure retrievals, it is necessary to determine the extent to which other constituents will interfere with the absorption of molecular oxygen. Several parameters can be derived simultaneously:• O2• O3• NO2• H2O
Figure 2. MANTRA balloon being filled with helium.
Figure 3. Solar occultation geometry.
Figure 7. Slant column amount of molecular oxygen from CPFM balloon flight, derived from measurements of the O2 B-band. Results have been scaled by a constant to fit modelled atmosphere. A solar zenith angle of approximately 96
degrees corresponds to a tangent height at the Earth’s surface.
Figure 6. Calibrated solar occultation spectra.
Figure 9. Vertical profile of ozone from ozonesondes and CPFM instrument.
Figure 8. Vertical profile of NO2 from CPFM instrument.
6. SUMMARY
• This work has resulted in the retrieval of slant column amounts of O2, O3, and NO2 from a balloon-based instrument similar to the MAESTRO satellite instrument.
• Vertical profiles of O3 and NO2 have been derived.
• Retrievals of O2 will be used for determining vertical profiles of temperature and pressure.
• Future work includes two planned launches of the MAESTRO engineering model on MANTRA flights in 2002 and 2003 for retrieval algorithm verification and satellite validation.
5. VERTICAL PROFILESVertical profiles were derived using a refractive non-linear optimal estimation routine.
O2 B-band
O2 γ-band
Scientific Objectives of the CPFM on the MANTRA Mission
• To investigate the feasibility of retrieving vertical profiles of temperature and pressure from the A and B bands of molecular oxygen in support of the MAESTRO project
• To assist in the continuing investigation of the odd nitrogen budget in the stratosphere by providing vertical profiles of ozone and NO2
photodiode
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concave holographic
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Meteorological Service of Canada